32-bit PCG random numbers, in C++

pcg32.hpp

// PCG-32 implementation: https://pcg-random.org/
// (c) 2026 Signalsmith Audio
// 0BSD Licence, or you can re-distribution with any license you like, just replace this line

#include <random>

struct Pcg32 {
	uint64_t state;
	static constexpr uint64_t multiply = 6364136223846793005ULL;
	uint64_t add;

	// This is the core of it, which gets the next 32-bit value
	uint32_t u32() {
		uint64_t prevState = state;
		state = prevState*multiply + add;
		auto xorShift = uint32_t(((prevState>>18)^prevState)>>27);
		auto rotateBits = uint32_t(prevState>>59);
		return (xorShift>>rotateBits)|(xorShift<<((-rotateBits)&31));
	}

	// Everything below this point is just for convenience

	Pcg32(uint64_t state, uint64_t add) : state(state), add(add|1) {}

	Pcg32() : Pcg32(std::random_device{}) {}

	template<class Uint32Source>
	Pcg32(Uint32Source &&seed) {
		state = uint64_t(seed());
		state |= uint64_t(seed())<<32;
		add = 1|uint64_t(seed());
		add |= uint64_t(seed())<<32;
	}
	
	// Results as other number types
	
	int32_t i32() {
		return static_cast<int32_t>(u32());
	}
	
	// [0, x)
	float uniform(float range) {
		return u32()*(range/0x100000000);
	}
	// [-x, x)
	float uniform2(float range) {
		return i32()*(range/0x80000000);
	}
	// [low, high)
	float uniform(float low, float high) {
		return low + u32()*((high - low)/0x100000000);
	}
};